Drug delivery system with profiles

ABSTRACT

An automatic injection device includes a drive mechanism and a sensor used to determine an internal characteristic such as a force or internal pressure generated during an injection process. This characteristic is then used as a control parameter by a microprocessor or controller which generates corresponding commands to the drive mechanism. In a particularly advantageous embodiment, the characteristic is used to calculate an exit pressure at which fluid ejected by the device through an elongated tube. The drive mechanism is then operated in such a manner that the exit pressure is maintained at a predetermined level to insure that a patient does not suffer pain and/or tissue damage.

RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional applicationSer. No. 60/081,388 filed Apr. 10, 1998.

BACKGROUND OF THE INVENTION

[0002] a. Field of Invention

[0003] The present invention relates generally to improvements to thedelivery of drugs, particularly to systems for subcutaneousinjection/aspiration (syringes) for drug delivery providingintermittent, episodic or limited drug delivery (as opposed tocontinuous drug delivery of syringe pumps). More specifically, thisinvention relates to an improved means of subcutaneous drug (fluid)injection and aspiration, providing a means and method of controllingand monitoring the interaction of specific flow rate and pressure duringfluid injection and aspiration with a hypodermic hollow-core needle.

[0004] b. Description of the Prior Art

[0005] Infusion pumps devices and systems are relatively well known inthe medical arts, for use in delivery or dispensing a prescribedmedication to a patient. These may be compact pump housings or largerstationary pump housing units. The administration of prescribed drugshas been described in the literature as administration to a patientthrough infusion tubing and an associated catheter or the like, therebyintroducing the drug intravenously. These systems have seen improvementsover time with respect to determining infusion line occlusion. Lineblockage would cause pressure in the syringe to increase. Systems in theprior art have been developed to identify a predetermined threshold orto monitor pressure to determine means for selecting ranges of occlusionpressures to insure patient safety. U.S. Letters Patents No. 5,295,967;4,731,058; and 5,080,653 show systems (with syringe pumps or the like)which are adequate for the intended use of intravenous drug delivery andmore specifically for monitoring occlusion during infusion. However,these systems do not provide a means for drug delivery subcutaneouslyvia a hypodermic needle. Moreover these systems do not provide a meansof aspiration during drug delivery, which is a medical requirement forsubcutaneous injection in an attempt to avoid intravascular placement ofthe hypodermic needle.

[0006] Pain, tissue damage and post-op complications have long beentolerated as negative side effects from the use of existing hypodermicdrug delivery injection systems. This is well documented in both thedental and medical literature. The pain and tissue damage are as adirect result of uncontrolled flow rate in conjunction with excessivepressures created during the administration of drug solutions within thetissue spaces. Subjective pain response of a patient has beendemonstrated to be minimized at specific flow rates during theadministration of a drug. Also, it has been scientifically demonstratedthat particular pressures (excessive without occlusion, per se) for aspecific tissue type will cause damage. It is therefore critical that aspecific flow rate in conjunction with a specified pressure range bemaintained during the delivery of fluids (drugs) when a subcutaneousinjection is given preventing subjective pain response as well as tissuedamage. It is also necessary that this system have the capability toaspirate under controlled conditions of rate and pressure to avoid thesame negative side effects during fluid movement. U.S. Pat. No.5,180,371 to Spinello, incorporated herein by reference, presented aninvention which allowed a rate to be set for the drug via a hypodermicneedle. That invention however did not disclose means of determining,detecting or monitoring pressure during the administration of a drug.

[0007] During the early 1980's, several researchers (See for instanceRood, The Pressure Created by Inferior Alveolar Injections, BritishDental J. 144:280-282 (1978); Walton and Abbot, Periodontal LigamentInjection; a Clinical Evaluation JADA.(Oct. 1981); Smith and Walton ,Periodontal Ligament Injection; Distribution of Injected Solution OralSurg 55:232-238 (1983)} clearly demonstrated and concluded that thepressure created by the injected fluid is critical to preventing tissuedamage and a pain response. Variability, different collagen types andconnective tissue densities results in different tissue compliance anddistensibility. These variations are found between subjects and withinthe individual subjects. Rood in his 1978 article states that “[t]herelationship between rate of injection and pressure rise seen clearlywith the smaller volumes was lost when 2.0 ml was injected. Several highpressures were recorded and some unexpected low ones. Many tracingsshowed a pattern suggestive of tissue disruption and it is possible thatsaid low pressures were due to the fluid no longer being containedwithin the pterygomandible space as the volume injected was similar tothe previously estimated volume of the tissue space.” Hence, it appearsthat the rate of flow is not directly related to pressure during aninterstitial injection. Smith and Walton described in their articleidentified supra discussed above that they have performed a histologicanimal study (canines) using a technique to calibrate manual pressuresproduced. They concluded that the “Volume injected and needle locationwere not always related to distribution. Injecting under moderate tostrong back pressure gave deeper and more widespread dye penetration.”This once again confirms that pressure is the critical variable in thedistribution of the solution within tissues and the volume is not alwaysrelated to the pressure produced.

[0008] Pashley, Nelson & Pashley in “Pressures Created by DentalInjections” (J Dent Res 1981) used a pressure transducer and fixed flowrate created by a motor driven traditional syringe clearly demonstratedthat different tissues have a different tissue compliance. Interstitialpressure variability was statistically and clinically significant evenwith a fixed flow rate. Therefore, it may be concluded that theyproduced great variations of pressure by using a metered flow rate.

[0009] Pertot and Dejou described in their article “Effects of the forcedeveloped during periodontal ligament injections in dogs” (Oral Surg.Oral Med, Oral Pathol. 1992) how they used a syringe coupled to aminiature force transducer and found a positive correlation between thenumber of osteoclasts and the force applied on the syringe plunger,which indicated the pressure generated in the PDL space enhancedosteoclastic activity. This experiment again indicates that pressure isa critical factor to tissue damage and is dependent on the resistanceencountered and not the flow rate of the solution into the tissues.

[0010] One of the goals of dentistry and medicine should be toadminister care to patients in the most humane and painless manner. Thesine qua non of any treatment is to produce a desired result withoutcausing damage or pain to the individual. Therefore there is animportant need in all fields of surgery for an injection system whichcan be used to administer a fluid while causing substantially no pain ortissue damage to the patient.

OBJECTIVES AND SUMMARY OF THE INVENTION

[0011] The present invention has for its objective to minimizesubjective pain response and any potential tissue damage to a patientresulting from of inappropriate pressures produced during theadministration of a drug via hypodermic needle.

[0012] A further objective is to provide these benefits using a varietyof different drug sources, i.e., standard syringes as well as,anesthetic cartridges or carpules.

[0013] A further objective is to provide a system which can be usedeasily by a clinician with very minimal training.

[0014] A further objective is to provide a system of the type discussedabove having a substantial disposable portion.

[0015] A further objective is a system which can provide not onlyinjections but also proper aspiration and/or biopsy with the capabilityto control both rate and pressure.

[0016] A further objective is to provide a system which automaticallydetermines and uses the exit (or entry) pressure as a control parameterfor any size and combination of syringe, tube or needle.

[0017] Prior art references are known which attempt to utilize apressure transducer to measure the pressure within the syringe (See forinstance U.S. Pat. No. 5,295,967). A major deficiency of these systemsis their inability to adjust the flow rate and/or pressure of the fluidto compensate for changes in resistances throughout the system, or tothe exit pressure. (Exit pressure refers to the fluid pressure justdownstream of the needle tip within the patient's body). Moreover, theprior art references fail to provide any means of determining this exitpressure. The present invention comprises a microprocessor-based systemwhich measures a pressure or force generated externally of the tissues,and then uses this measurement to accurately determine the correspondingexit pressure. In other words, by using specific software, the systemmonitors the exit pressure and generates and maintains a specific flowrate even when there are changes in the resistance of the system.

[0018] The invention also provides a system which automaticallycompensates for the total resistance encountered within the system andwhich has been proven to influence flow rates and measured pressure. Itis believed that this is the first system which has the capability toprovide a precisely defined flow rate and desired pressure by takinginto account the total system resistance. It is submitted that withoutthis capability, flow rates and exit pressures cannot be preciselyderived for varying disposable assemblies consisting of differentsyringe, tubing, needle sizes and fluid characteristics. A criticalfeature of the system is that it controls and monitors the pressureusing a transducer that generates a feedback parameter.

[0019] Briefly, a system in accordance with this invention fordispensing a fluid by injecting the same into a patient includes amechanical assembly and an electrical controller. The mechanicalassembly consists of a drive mechanism and a disposable portionconsisting of a fluid storage device such as a syringe, a carpule andthe like, and a fluid delivery section including a tube coupled to saidfluid storage device and terminating in a needle adapted to be insertedinto the subject tissue. The drive mechanism includes a housing with aninternal motor and a mount for mounting the fluid storage device on thehousing. The fluid storage device includes a reciprocating plunger. Acoupling is used to move the plunger with said motor. Importantly, atransducer is used to sense the force or pressure generated by the motorand applied by the plunger within the fluid storage device. If a carpuleis used for the fluid storage device, an adapter is also provided toallow the same mount to secure the carpule as well. The mount isarranged and constructed to secure syringes or carpules having a largevariety of sizes. The motor, the coupling associated with the motor andthe electronic controller discussed below is at least partially disposedwithin the housing for protection.

[0020] The electrical controller is provided for controlling the overalloperation of the system. The controller includes a master microprocessorwhich may be provided as a standard stand-alone PC or laptop PC, and aninternal slave microprocessor operating in response to commands from themaster microprocessor. The master microprocessor provides theinterfacing with the clinician and collects data regarding themechanical assembly. The master microprocessor is also associated with adisplay used to provide instructions to a clinician and an input device,which may be a keyboard, a touch screen or voice-activated device tocollect information from the clinician. The master microprocessor isfurther associated with a memory which holds several data banks, eachdata bank being associated with one of the elements of the disposableportion as well as other parameters.

[0021] The fluid storage device is filled and a setup process isinitiated during which various operational parameters are calculated,retrieved or received from the clinician. The clinician also specifiesthe fluid flow rates and peak exit pressure and a total amount of fluidto be dispensed. Then he operates a pneumatic control such as a footpedal and initiates the fluid flow. Alternatively, commands may beinitiated by the clinician either electronically or by voice commands.During dispensing, the output from the transducer is used to calculatethe current exit fluid pressure. If this exit pressure approaches acertain threshold, the fluid flow rate is automatically reduced toprevent excessive exit pressure, thereby ensuring that the patient doesnot suffer undue pain and no tissue is damaged. Several optionalfeatures are also provided including aspiration, purging or charging themedia with or without air.

[0022] Alternatively, the system may be operated in a biopsy mode inwhich the entry pressure and the outbound or withdrawn fluid flow rateare the relevant control parameters.

[0023] Throughout the process, the clinician is provided with constantcurrent information on the ongoing process, both visual and aurally,including the current flow rate, total volume ejected or aspired, exitor entry pressures and other parameters. The slave microprocessorreceives commands from the master microprocessor and generates the drivesignals required to operate the motor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 shows a diagram illustrating the major components of themechanical system for the present invention;

[0025]FIG. 2 shows an orthogonal view of the drive mechanism;

[0026]FIG. 3 shows the major elements of the drive mechanism;

[0027]FIG. 4 shows how the elements of the drive mechanism of FIG. 3 aredisposed in the housing;

[0028]FIG. 5A shows a top view of the housing without the bracket;

[0029]FIG. 5B shows an orthogonal view of the housing without thebracket;

[0030]FIG. 6 shows an elevational view of a clamp for securing a syringeto the housing;

[0031]FIG. 7A shows a top view of the platform 30 of FIG. 2;

[0032]FIG. 7B shows a side elevational view of the platform 30 of FIG. 2and 6;

[0033]FIG. 8 shows a side sectional view of a prior art cartridge for afluid;

[0034]FIG. 9 shows a somewhat diagrammatic side view of an adapter forusing the cartridge of FIG. 8 with the system of FIGS. 1-7;

[0035]FIG. 10 shows a block diagram of the electronic controller;

[0036]FIG. 11 shows a general flow chart for the operation of thecontroller of FIG. 10;

[0037]FIG. 12A shows a typical display showing various possible choicesfor the elements of the disposable portion;

[0038]FIG. 12B shows a typical display summarizing the operationalcharacteristics and parameters of the current procedure;

[0039]FIG. 13 shows a typical display shown to the clinician during thesetup process;

[0040]FIG. 14 shows graphically the control signals derived from a footpedal;

[0041]FIGS. 15A and 15B show typical time dependent curves for the fluidflow and the exit pressure, respectively;

[0042]FIGS. 16A and 16B show time dependent curves for fluid flow andthe exit pressure when said pressure exceeds a threshold level;

[0043]FIG. 17 shows a flow chart for aspiration;

[0044]FIG. 18 shows a flow chart for charging a syringe;

[0045]FIG. 19 shows the syringe and associated equipment required forcharging; and

[0046]FIG. 20 shows a flow chart for determining a typical componentcontributing to the exit pressure determination.

DETAILED DESCRIPTION OF THE INVENTION

[0047] The subject invention pertains to a system for delivering drugssuch as an anesthetic, or to provide aspiration, for example for abiopsy, in an efficient manner which insures at the same time that painto the patient is minimized. The system includes a mechanical assemblycooperating with an electronic controller.

[0048] The mechanical assembly is illustrated in FIGS. 1-9 and theelectronic controller 150 is shown in FIGS. 10-18.

[0049] A drug delivery system 10 constructed in accordance with thisinvention includes drive mechanism 12, a delivery tube 14 and a handle16 terminating with a needle 17. More particularly, a syringe 90 (orother fluid storage device) is mounted on the drive mechanism with oneend of tube 14 being coupled to the syringe 90. The drive mechanism 12operates a plunger 94 to selectively eject fluid out through the tube 14handle 16, and needle 17 or alternatively to draw fluid in. The drivemechanism 12 is associated with an external controller for selectingvarious operational parameters discussed in more detail below. Thisexternal controller may be provided on the housing of the drivemechanism or may be provided as a separate control unit 18 coupled tothe drive mechanism 12 by a cable 20. The control unit 18 may be forinstance a PC or laptop computer. Alternatively, the control unit 18 maybe internal.

[0050] Details of the drive mechanism 12 are seen in FIGS. 2-5. Startingwith FIG. 2, drive mechanism 12 includes a housing 22 with a top surface24 and intermediate surface 26 disposed below top surface 24. On surface26 there is formed a rail 28 extending along the longitudinal axis ofhousing 14. A platform 30 which is disposed on the rail 28 can bereciprocated back and forth in parallel with said longitudinal axis, asdescribed in more detail below.

[0051] On top surface 24, as seen more clearly in FIGS. 5A and 5B, thereare provided two parallel elongated slots 32 and 34 and in between theseslots there is formed a groove 36. The ends of each of the slots havelateral extensions 38 facing toward each other. Groove 36 ends adjacentto a transversal slot 54.

[0052] Riding in slots 32, 34 is a clamp 40. As seen in FIG. 6, clamp 40has a generally C-shaped body 42 terminating in legs 44 extending towardeach other, and a web 46. A screw 48 with a head 50 extends through athreaded hole (not shown) in web 46 and terminates in a pad 52.

[0053] Clamp 40 is constructed and arranged so that its legs 44 fit intoextensions 38 and allow the clamp to ride horizontally in slots 32, 34.

[0054] Platform 30 (seen in more detail in FIGS. 7A and 7B) is formed onits top surface 58 with a slot 56, which is provided on one side with agraduated keyway 60.

[0055] Inside the housing 22, there is provided a motor 66 (FIGS. 3 and4) held securely within the housing. Threaded through the motor 66 thereis a worm screw 72. The worm screw 72 is arranged so that as the motor66 is activated, the worm screw 72 moves in one direction or another,dependent on its direction of rotation, in parallel with thelongitudinal axis of the housing 22. One end of the worm screw 72 isnon-rotatably attached to a pad 74, coupled to a platform 76. Disposedbetween platform 76 and pad 74 there is a load cell 78 arranged totransmit and measure the force between the pad 74 and platform 76. Theload cell 78 is bidirectional so that it can measure both stress andstrain dependent on whether the worm screw 72 is moving to the left orto the right as determined in FIG. 3. Two short rods 80 are used tocouple the pads 74 to platform 76, to prevent the transmission ofrotational forces generated by the motor 66 to the platform 76.

[0056] Two columns or rods 82, 84 extend between platforms 30 and 76 andsecure these two members together. These rods 82, 84 are slidablysupported by two pairs of bushings 68, 70 on the housing 22. Except forthese bushings, the platforms 76 and 30 are floating respectively insideand outside the housing 22. Rods 82, 84 extend through wall 86 extendingbetween surfaces 24 and 26 via holes (not shown). The rail 28 is hollowand aligned with the worm screw 72 to allow the worm screw 72 to movelongitudinally along its axis through the housing 22.

[0057] Typically, the syringe 90 has a barrel 92 positioned in groove 36so that its finger tab 95A (seen in FIG. 6) rests in slot 54. Thesyringe 90 also includes a plunger 94 reciprocated within the barrel 92by a shaft 93. The shaft terminates in a finger pad 96. When the syringe90 is seated in groove 36, the finger pad 96 rests in slot 58 ofplatform 30. In this position, the syringe 90 is secured to the housing22 by inserting the legs 44 of clamp 40 into slot extensions 38 andadvancing or sliding the clamp 40 to the left over the syringe 90 untilit is positioned at the end of the syringe body 92 adjacent to the slot54. In this position, the screw 50 is tightened, forcing the pad 52 toadvance and engage the barrel of syringe 90. The groove 36 assists inthe positioning of the syringe 90. The syringe terminates with a Luerlock 95 used to connect the syringe to tube 14.

[0058] It should be appreciated that the motor 66, pad 74, load cell 80,worm screw 72 and platform 76 are all located within housing 22.Platform 30 is disposed outside the housing 22. When the motor 66 isactivated, as discussed below, it forces the worm screw 72 to move inone direction or another. The worm screw in turn forces the platforms30, 76 and rods 82 and 84 to move in concert as well, thereby forcingthe plunger 94 to move. The only elements which move in and out of thehousing are the rods 82, 84. Hence most of the critical elements of thesystem are protected within the housing from tampering, or spilledfluids. Moreover, the drive mechanism 12 is adapted to receive andoperate with syringes of various diameters and lengths. Similarly, thedelivery tube 14, handle 16 and needle 17 may have any size desired.

[0059] In the embodiment discussed so far, it is assumed that a fluid isdispensed from the syringe 90 and, therefore, this syringe 90 must bepreloaded with said fluid either by the manufacturer, or must be filledat the site by the clinician or an assistant prior to the start of anyoperation. In many procedures, however it is more desirable to providethe fluid to be dispensed in a cartridge such as cartridge 100 shown inFIG. 8. As can be seen in this FIG., cartridge 100 consists of acylindrical barrel 102. At one end, the barrel 102 is provided with aplunger 104 made of rubber or a similar resilient material which can bereciprocated through the barrel 102 to selectively eject the liquidcontained therein. At the opposite end, the cartridge is provided with aseal formed of a membrane 106 which must be pierced before the contentsof the cartridge can be dispensed.

[0060]FIG. 9 shows an adapter 110 provided to allow the driver of FIGS.1-7 to dispense a fluid from cartridge 100. The adapter 110 includes aholder 112 adapted to hold cartridge 100. Holder 112 includes a firstend having a connector 114 (for example a Luer connector) to connect theadapter 10 to delivery tube 14. Inside the holder 112, adjacent toconnector 114, there is a spike 116 constructed and arranged to piercethe membrane 106 when the cartridge 100 is inserted into the holder 112.At the opposite end, the holder 112 is provided with radially extendingprojections 118 to secure the holder 112 to a drive mechanism 12. Thecartridge holder 112 described so far is disclosed in commonly assignedcopending application Ser. No. 09/028,009 filed Feb. 23, 1998 entitled“Dental Anesthetic and Delivery Injection Unit” incorporated herein byreference.

[0061] Adapter 110 further includes a coupling element 118 formed of ashaft 120 terminating at one end with a barb or hook 121 and at theopposite end with a thumb pad 122. The shaft 120 passes through a cap124 adapted to mount on holder 112 by projections 116 engagingcorresponding depressions (not shown) in the cap 124. Cap 124 isprovided with a tab 126 extending radially and having the approximateshape of finger tab 95A on a standard syringe 90.

[0062] In order to mount cartridge 100 on the drive mechanism 12, thecartridge 100 is first inserted into the holder 112 from its rear end.Once the cartridge 100 is seated inside the holder 112, the shaft 120 ispositioned in longitudinal alignment with the axis of holder 112 andthen its hook 121 is pushed into the piston 104 until it is firmlyengaged therewith. Next, the cartridge 100 is advanced toward theconnector 114, so that the spike 116 penetrates the membrane 106 therebyproviding an egress for the fluid contained therein. In order to ensurethat the fluid does not spill, the tube 14 may be mounted on connector114 first, however, this tube has been omitted in FIG. 9 for the sake ofclarity.

[0063] Instead of a hook, a plunger 121 A may be secured to the shaft120 in such a manner that when this plunger is inserted into the holder112, a vacuum/pressure coupling is generated between it and the piston104. As a result, the longitudinal movement in either direction of theplunger causes the piston 104 to follow and thereby either push fluidinto or out of the system.

[0064] Next, the cap 124 is coupled to the holder 112 by pushing theprojections 116 into the appropriate depressions in the cap 124, therebysecuring the cap to the holder 112. In this configuration, the cartridge100, and adapter 110 have a configuration similar to a syringe 90 andcan be mounted on the drive of FIGS. 1-7 just like a syringe, with theclamp 40 engaging cap 124, tab 126 extending into the slot 54, and thumbpad 122 engaging slot 56 on platform 30. With the adapter 110 in thisposition, motor 66 can be used to advance or retract shaft 120 andpiston 104 into or out of the cartridge 100 either via the hook 121 or aplunger thereby causing the fluid to be ejected or aspirated as desired.The hook 121 (or the plunger) formed on the end of the shaft 120 isprovided to ensure proper engagement and a solid mechanical coupling ofthe shaft 120 to piston 104 thereby ensuring that the piston 104 followsthe movement of the shaft 120 and platform 30 in either direction.

[0065]FIG. 10 shows a block diagram of the electronic controller 150.The controller 150 includes two microprocessors: a master microprocessor152 and a slave microprocessor 154. Slave microprocessor 154 is used toderive the signals that actually drive the motor 66 and to collectinformation regarding the position of the platforms 30, 76.

[0066] The master microprocessor 152 is used to collect informationregarding the rest of the system, including the syringe 90, and itscontents, the tube 14, the handle 16 and so on, and to generate controlsignals for the slave microprocessor 154 necessary for operating themotor 66 to deliver the contents of the syringe 90.

[0067] Physically, the slave microprocessor 154 and its associatedcircuitry are disposed within the housing 22. The master microprocessor152 is incorporated into control unit 18 which is coupled to the housing22 through cable 20 as shown in FIG. 1.

[0068] As seen in FIG. 10, microprocessor 152 is associated with amemory 160, input devices 162, display devices 164 and an interface 164.

[0069] Memory 160 is used to store programming and data for the mastermicroprocessor 152. More specifically, the memory 160 is used to storesix or more data banks, each of said data banks being dedicated to thefollowing information: (a) syringes; (b) tubing; (c) needles; (d)fluids; (e) governor parameters; and (f) profiles consisting of aplurality of parameters for a particular procedure to be performed. Eachof these parameters is used to determine the control signals generatedfor the slave microprocessor 154. Each of these data banks contains theappropriate parameters for various commercially available products, oralternatively, parameter data derived using a specific algorithm.Information regarding the various elements for a particularconfiguration is entered through input devices 102 and is confirmed onthe display device 164. These input devices may include a keyboard, atouch screen, a mouse, as well as a microphone. If a microphone isincluded, voice commands are interpreted by a voice recognition circuit162A.

[0070] The display device 164 is further used to provide an indicationas well as instructions on the operation of the system 10. The commandsfor the operation of motor 66 are generated by master microprocessor 152and transmitted to an interface 162. Microprocessor thereby causing thefluid to be ejected or aspirated as desired. The hook 121 (or theplunger) formed on the end of the shaft 120 is provided to ensure properengagement and a solid mechanical coupling of the shaft 120 to piston104 thereby ensuring that the piston 104 follows the movement of theshaft 120 and platform 30 in either direction.

[0071]FIG. 10 shows a block diagram of the electronic controller 150.The controller 150 includes two microprocessors: a master microprocessor152 and a slave microprocessor 154. Slave microprocessor 154 is used toderive the signals that actually drive the motor 66 and to collectinformation regarding the position of the platforms 30, 76.

[0072] The master microprocessor 152 is used to collect informationregarding the rest of the system, including the syringe 90, and itscontents, the tube 14, the handle 16 and so on, and to generate controlsignals for the slave microprocessor 154 necessary for operating themotor 66 to deliver the contents of the syringe 90.

[0073] Physically, the slave microprocessor 154 and its associatedcircuitry are disposed within the housing 22. The master microprocessor152 is incorporated into control unit 18 which is coupled to the housing22 through cable 20 as shown in FIG. 1.

[0074] As seen in FIG. 10, microprocessor 152 is associated with amemory 160, input devices 162, display devices 164 and an interface 164.

[0075] Memory 160 is used to store programming and data for the mastermicroprocessor 152. More specifically, the memory 160 is used to storesix or more data banks, each of said data banks being dedicated to thefollowing information: (a) syringes; (b) tubing; (c) needles; (d)fluids; (e) governor parameters; and (f) profiles consisting of aplurality of parameters for a particular procedure to be performed. Eachof these parameters is used to determine the control signals generatedfor the slave microprocessor 154. Each of these data banks contains theappropriate parameters for various commercially available products, oralternatively, parameter data derived using a specific algorithm.Information regarding the various elements for a particularconfiguration is entered through input devices 102 and is confirmed onthe display device 164. These input devices may include a keyboard, atouch screen, a mouse, as well as a microphone. If a microphone isincluded, voice commands are interpreted by a voice recognition circuit162A.

[0076] The display device 164 is further used to provide an indicationas well as instructions on the operation of the system 10. The commandsfor the operation of motor 66 are generated by master microprocessor 152and transmitted to an interface 162. Microprocessor 152 is furtherprovided with a speaker 165 used to provide various oral messages,including spoken pre-recorded or synthesized words, (generated by avoice synthesized circuit 165A) chimes, and so on, to provideinstructions to the clinician and to provide other information about thecurrent status of the whole system and its elements without the need forthe clinician to look at the displays all the time.

[0077] The slave microprocessor 154 receives these commands throughcable 20 or other connection means and interface 170.

[0078] Also associated with the slave microprocessor 154 are one or moreposition sensors 172 and a chopper drive circuit 174. As previouslymentioned, the force between platform 76 and pad 74 is measured by aload cell 78. This load cell may be for instance a Model S400 load cellmade by the SMD, Inc. of Meridien, Connecticut.

[0079] Also associated with slave microprocessor 154 is a foot switch orpedal 176. Preferably foot pedal 176 consists of an air chamber with aflexible side wall, said side wall being arranged to change the volumeof air and pressure within said chamber in response to activation by ahuman operator. A pressure sensor (not shown) is part of the foot pedaland is arranged to provide information about said pressure to slavemicroprocessor 154 via a corresponding AID converter 190. Foot pedals ofthis kind are well known in the art and therefore its details have beenomitted.

[0080] The sequence of operation for the system 10 is now described inconjunction with FIG. 11. Starting in step 300, the system is first setup. Since this step involves exchange of information with the clinicianand the outside world, it is performed by the master microprocessor 152.

[0081] Step 300 involves, first, having the clinician enter thefollowing information: type of syringe being used, type (i.e. size andlength) of tube 14, type of needle being used, and name or otheridentification of the fluid in the syringe. This information may beentered manually by the clinician using an input device such as akeyboard or a touch screen disposed in the screen. Alternatively, aplurality of the corresponding items (for example, syringes) may beretrieved and displayed from the data bases and then presented to theclinician. The clinician then uses a standard pointing device such as amouse or a touch screen to select the appropriate syringe. Alternativelya voice command may be used for this selection. FIG. 12 A shows atypical screen for designating or selecting a syringe. As seen on thisscreen, once a syringe is selected or designated, its physicalcharacteristics such as length, nominal volume, stroke length, syringeforce are retrieved from the data bank and displayed. After the needleand fluid have been designated, their characteristics are retrieved anddisplayed as well.

[0082] Some of the information, such as, for instance, the length of thetube 14 must be entered manually since it would be difficult for thesystem to determine. However other information, as well as variousoperational parameters are determined automatically. For example, theidentify of a syringe may be encoded into a portion of the syringe andread by the system. As described below, one required parameter is thecross sectional area A of the syringe. This is determined by dividingthe volume by the stroke or length of the syringe.

[0083] Once the information regarding the components of the system areentered or otherwise selected, another screen (FIG. 12B) is presented tothe clinician. This screen is used to either provide information to theclinician or to allow the clinician to enter certain additionaloperational parameters required to complete the setup.

[0084] The screen of FIG. 12B has five general areas designated 502,504, 506, 508 and 510. In area 502, some general information is providedor selected by the clinician including a designation for the profile tobe used for the current procedure, i.e. ‘PERIODONTAL LIGAMENTINJECTION’. In area 504, the parameters from screen of FIG. 12A arerepeated in an abbreviated format, thereby indicating the syringe,needle, tube and fluid information.

[0085] In area 506 the clinician selects the type of operation herequires (i.e., injection) the high and low flow rates, and the optimalpressure limit. As previously mentioned, this last parameter is veryimportant because it controls the amount of pain and tissue damage thatthe patient may suffer during the procedure. Additional parameters mayalso be selected in this area, such as charge flow rates, aspirationvolume and flow rate, purge volume and flow rate and so on.

[0086] In area 508 the clinician designates the total amount of fluid tobe dispensed, and whether (a) the syringe is charged, (b) is to becharged with air; or (c) to be charged without air. The clinician alsoselects in this area whether he will use aspiration or not. Finally area510 is used to indicate various parameters calculated from theinformation previously received or selected, including the systemvolume, maximum flow rates, maximum pressure and so on.

[0087] In one embodiment of the invention, the system, and moreparticularly the master microprocessor 152 then uses these parameters toretrieve from the profile data base a profile which determined thesequence and programming characteristics required to deliver the fluidto through the needle at the requested, or optimized rate. The profilefor each particular syringe-tube-needle combination is calculated andstored into the memory earlier. These profiles have uniquecharacteristic for each type of surgical procedure. For example, aprofile for a PDL (periodontal ligament) is different from a profile fora cranial subcutaneous anesthesia delivery. Only a single group orfamily of profiles' associated with a specific procedure may be storedin the memory of the master microprocessor since other such profiles aresuperfluous.

[0088] Alternatively, the master microprocessor 152 may be programmed toperform the calculations necessary to generate the profiles. However itis expected that for most applications, the profiles will be calculateda priori and programmed or stored into the data base, as discussedabove.

[0089] After the setup procedure is completed, in step 302, a test isperformed to determine if the clinician desires to fill the syringe 90using the subject device or not. In many instances, it is expected thatthe clinician either preloads the syringe manually, or uses a prefilledsyringe or cartridge. If the syringe is loaded or charged off thedevice, then in step 304, the master microprocessor 152 sends a commandto the slave microprocessor 154 to move the platform 30 to an initialposition.

[0090] Referring to FIG. 10, the microprocessor 154 is associated withthe load cell 80 through an A/D converter 83, a Ram 182, an EEPROM 184,and a limit switch 172. Using information derived from these elements,whose functions are described in more detail below, and in response tocommands from the master microprocessor 152 via interface 170, the slavemicroprocessor 154 controls the operation of motor 66. More specificallythe slave microprocessor 154 operates a chopper drive circuit 188 whichthen generates stepping pulses to motor 66 to cause said motor 66 toturn in one of two directions by a discrete angular increment. Thefrequency of these pulses determines the speed of the motor. Separatespeeds may be used for high flow rate, low flow rate purge, aspirationor charging. The clinician selects the values for all these speedparameters and the microprocessor then calculates the correspondingmotor speed (i.e. step frequency) using the dimensions of the syringeand the fluid delivery system.

[0091] In one embodiment of the invention, the system, and moreparticularly the master microprocessor 152 then uses these parameters toretrieve from the profile data base a profile which determined thesequence and programming characteristics required to deliver the fluidto through the needle at the requested, or optimized rate. The profilefor each particular syringe-tube-needle combination is calculated andstored into the memory earlier. These profiles have uniquecharacteristic for each type of surgical procedure. For example, aprofile for a PDL (periodontal ligament) is different from a profile fora cranial subcutaneous anesthesia delivery. Only a single group orfamily of profiles associated with a specific procedure may be stored inthe memory of the master microprocessor since other such profiles aresuperfluous.

[0092] Alternatively, the master microprocessor 152 may be programmed toperform the calculations necessary to generate the profiles. However itis expected that for most applications, the profiles will be calculateda priori and programmed or stored into the data base, as discussedabove.

[0093] After the setup procedure is completed, in step 302, a test isperformed to determine if the clinician desires to fill the syringe 90using the subject device or not. In many instances, it is expected thatthe clinician either preloads the syringe manually, or uses a prefilledsyringe or cartridge. If the syringe is loaded or charged off thedevice, then in step 304, the master microprocessor 152 sends a commandto the slave microprocessor 154 to move the platform 30 to an initialposition.

[0094] Referring to FIG. 10, the microprocessor 154 is associated withthe load cell 80 through an A/D converter 83, a Ram 182, an EEPROM 184,and a limit switch 172. Using information derived from these elements,whose functions are described in more detail below, and in response tocommands from the master microprocessor 152 via interface 170, the slavemicroprocessor 154 controls the operation of motor 66. More specificallythe slave microprocessor 154 operates a chopper drive circuit 188 whichthen generates stepping pulses to motor 66 to cause said motor 66 toturn in one of two directions by a discrete angular increment. Thefrequency of these pulses determines the speed of the motor. Separatespeeds may be used for high flow rate, low flow rate purge, aspirationor charging. The clinician selects the values for all these speedparameters and the microprocessor then calculates the correspondingmotor speed (i.e. step frequency) using the dimensions of the syringeand the fluid delivery system.

[0095] The microprocessor 154 keeps track of the position of theplatforms 30, 76 by counting the steps taken by motor 66. Alternatively,or in addition, other sensor switches may also be provided to detect andconform the location of the platforms, such as platform 76 at severallocations along its path of travel. In the preferred embodiment, atleast one sensor switch 172 is provided which defines the home positionfor the platform 76. All other positions of the platform 76 are computedfrom this home position. For example the home position could the extremeleft position shown in FIG. 4.

[0096] Motor 66 is preferably made with rare earth permanent magnets sothat it can be relatively compact and yet generate a large torque.

[0097] Getting back to FIG. 11, in step 304, the microprocessor 152sends a command to order the microprocessor 154 to move the platform 76to the home position. A list of all commands of this type is stored inthe memory 160 as part of the governor data base. The microprocessor 154activates the motor until the platform 76 reaches the home position, andthis position is verified by an output from sensor 172 and is reportedto microprocessor 152. Next, in step 306, microprocessor 152 orders theplatform 76 to be moved to an initial position. This initial position isa function of the selected syringe and the amount of fluid contained inthe syringe, and is defined by the profile stored in the profile database.

[0098] The system 10 is now ready to accept a filled syringe. FIG. 13shows a typical screen on display 164 which may be shown to theclinician at this time. This display includes a several soft orprogrammed ‘buttons’ which may be activated by the clinician to initiatecertain commands as well as several display regions in which informationis provided to the clinician. In this particular instance, the displayshows the following buttons 198 labeled: Quit, Print, Pedal. In otherinstances other buttons may be shown.

[0099] In addition, the display of FIG. 13 includes the followinginformation areas: a message area 200 in which instructions are providedfor the next phase; or a message is displayed informing the clinician ofthe step or processes being currently performed; two graphs 202, 204 inwhich the fluid flow and the exit pressure are shown as a function oftime, a syringe icon 206, a pressure gauge 208 which shows the currentexit pressure as a percentage of the maximum allowable pressure (anotherparameter developed as part of the profile), and another set of gaugescollectively marked 210 and indicating the following parameters:location of the platform 76 (and therefore the plunger within thecylinder) in inches with respect to the initial location, the volume offluid that has been injected (or collected in case of biopsy), thecurrent flow rate in cc/sec, the current pressure (psi), the force beingapplied and the force being applied by the pedal switch 176. At thebeginning of step 306, the display areas 202, 204, 208 and 210 show novalues for the corresponding values and the icon 206 has an indication212 to show that no syringe has been detected. Display 200 shows amessage instructing the clinician to load the syringe 90 and depress thepedal 176.

[0100] The clinician can now take a filled syringe and place in groove36 with the finger tab 95A extending into slot 54 and the thumb tab 96inserted into the slot 56 of platform 30. As mentioned before, the motor66 has moved the platforms 76, 30 to the initial position. This initialposition is defined as the position at which the filled syringe 90 canbe mounted with its thumb pad 96 fitting into the slot 56. It should benoted that the system will not accept syringes in any other position. Ineffect, the software is used to ensure that the correct syringe with thecorrect amount of fluid is loaded, and that another syringe cannot beloaded by mistake.

[0101] The system waits for the syringe to be mounted in step 310. Theclinician can indicate that the syringe is mounted either by activatingphysically foot switch 176 momentarily or activate the pedal button 198on the screen. When the pedal signal is sensed the drug delivery canproceed. First the red stop symbol 212 is turned off. In step 312 thesystem checks if the clinician has requested a purge. If so, a purge isperformed in step 313 during which the drug delivery system is freed ofpotential air bubbles. The volume of the needle, the handle and tube areknown and therefore the volume of fluid to be purged is easilycalculated.

[0102] As mentioned above, preferably, the foot switch 176 includes anair bellows and an air pressure sensor (not shown). The output of theair pressure sensor is fed to the A/D converter 190 and the digitalequivalent of the foot switch output is fed to the microprocessor 154.The microprocessor 154 uses this sensor in conjunction with a look-uptable stored in the EEPROM 184 to determine or generate a switchindication signal indicative of the position of the switch. It has beenfound that, for best response and sensitivity, the position of switch istranslated into four different positions or states using hysterisis. Inother words, as indicated in FIG. 14, initially the switch is in an idlestate. As the switch is depressed, its internal pressure increases. Whenit reaches a first value ONI, the microprocessor 154 generates a LOWFLOW command. If the pressure increases but does not exceed a level ON2then, the LOW FLOW command is maintained. If the pressure is reduced tobelow a level OFF1, then the idle state is indicated. Typically thepressure OFF1 is lower than ON1.

[0103] If the pressure exceeds ON2 then a HIGH FLOW command isgenerated. This HIGH FLOW command is not turned off until the pressuredrops below a pressure level OFF2 which is lower than ON2.

[0104] Referring back to FIG. 11, after purging, if any, in step 314position or state of the pedal 176 is determined. If a LOW FLOW commandis received, then the drug is dispensed at a low rate. If a HIGH FLOWcommand is received, the drug is dispensed at a high flow rate. Theactual values for HIGH and LOW FLOWS have been previously set asdiscussed above.

[0105] Once the pedal is depressed, the motor is initiated and is run ata predetermined rate corresponding to the rate of flow requested (step316). A typical drug delivery is shown in FIGS. 15A and 15B as theywould appear in areas 202 and 204 respectively. As seen in these FIGS.The flow rate builds up relatively quickly to a first value LOW at TOand levels off to a constant level. The exit pressure starts climbing ina somewhat irregular manner determined by the tissue resistance to thefluid flow and other factors. At TI the pedal is activated to a higherlevel HIGH and the fluid flow rate climbs to this new rate. The exitpressure continues to rise as well. At T2 the pedal may be released backto the lower level LOW. As this process continues, the microprocessor152 continuously monitors various pressure parameters (step 318), and itaccumulates the total volume dispensed and compares this current volumeto the total requested volume (step 320). If it has not been reached,then in step 322 a check is performed to determine if the pedal 176 isstill pressed. If it is, then step 314 is repeated. If it is not, thenit is assumed that an aspiration is requested, and accordingly anaspiration routine is performed as described below in conjunction withFIG. 17.

[0106] In step 318 the current pressure indicated by the load cell ischecked against a threshold which is the peak pressure that is safe forthe system. This pressure level depends on the components selected forthe system. In addition, in step 318 the exit pressure level is alsomonitored. As discussed above, it has been found that the fluid pressureduring an injection plays a very important role in the amount of painand tissue damage that a patient feels during an injection. At lowlevels of pressure, the pain is minimal so that the patient is almostcomfortable. However, if the pressure increases beyond a certain level,the injection becomes very painful. Therefore an important considerationin the present invention is the control of the flow rate in a mannerthat ensures a low exit pressure level.

[0107] More particularly, in step 318 if either pressure (i.e., thepressure within the system or the exit pressure) is found to beexcessive, then in step 324 the flow rate is reduced. In step 326 thepressures are checked again. If either pressure is still too high, theflow rate is reduced again in step 324. If acceptable, then the flowrate is resumed in step 328 and the process continues with step 320.

[0108] The flow rate and various other parameters are shown to theclinician on display shown on FIG. 13 so that he should be able to seevery easily what is happening. In all likelihood, an increase inpressure such as shown in FIGS. 16A and 16B at TX is caused either by ablockage or the needle hitting a bone. Whenever an abnormal pressure isdetected, a visual as well as an audible alarm is provided. Thereforethe clinician is expected to take some evasive action to stop the highpressure. However, if the blockage continues and the pressure keepincreasing the flow rate is gradually decreases as seen in FIG. 16Auntil it stops altogether.

[0109] Getting back to step 320, when the designated volume has beenreached or if a stop command is issued by the clinician, in step 330 anend subroutine is performed. During this subroutine, the forward motionof the syringe plunger stops, and a message is displayed for theclinician to withdraw the needle. The clinician can withdraw the needle,decouple the tube 14 from the syringe 90 and throw the tube 14 thehandle 16 and needle 17 away. Optionally, an aspiration subroutine,discussed below is also performed to ensure that fluid from the needle17 does not spill.

[0110] In many instances, aspiration is desirable during a drug infusionprocess. For example, for the infusion of an anesthetic, after theinsertion of the needle, aspiration is required to check if the needletip is disposed in a blood vessel. In this instance, aspiration causessome blood to be withdrawn from the vessel. This blood becomes visiblein the handle 16 or the hub of the needle 17.

[0111] As seen in FIG. 11, if in step 322 the pedal is found released,an ASPIRATE routine is initiated as shown in FIG. 17.

[0112] More particularly, in step 400 a check is performed to determineif the plunger 94 in the syringe 90 is stopped. If it is not then instep 402 a check is performed to determine if the plunger is moving at alow speed. If it is, then in step 404 low speed stop routine isperformed to slow down and stop the motor. Otherwise in step 406 a highspeed stop is routine is performed to slow down and stop the motor.

[0113] In step 408 a check is performed to determine if there issufficient clearance to perform an aspiration. Referring to FIG. 3, atthe moment an aspiration command is received, the plunger 94 could be inits rightmost position so that retreating it further from the syringemay cause it to fall out. Obviously such an event is not desirable.Therefore, in step 408 a check is performed to determine from thelocation of the plunger and the length of the syringe whether it is safeto perform an aspiration without the plunger falling out. If it is not,then the process is stopped and in step 410 an error message isdisplayed to the clinician to indicate that it is unsafe to aspire atthis time.

[0114] Otherwise in step 412 the motor is reversed and runs in theopposite direction for a predetermined time causing the plunger 94 toretract. After the plunger is moved the predetermined distance, it isstopped (step 414). The plunger is then moved forward again (step 416 )until it is returned to its original position at step 408. The motor isthen stopped (step 418).

[0115] Steps 416 and 418 may be omitted if the aspiration is performedat the end of the process when the needle is retracted from the tissue.

[0116] In this manner the subject system is used to deliver ananesthetic for a particular procedure. For example, if the procedure isa periodontal ligature then the following parameters are applicable:Syringe type: Dental Cartridge Syringe size:   1.8 cc Drug: LocalAnesthetic (Lidocaine HCl 2%, and epinephrene 1:100,000) Specific weightof drug: 0.0361 Tube inner diameter:  0.015 in Tube length:    60 inNeedle type: BD 30 G ½ Needle length:   0.5 in Needle inner diameter: 0.006 in Low Speed: 0.0059 cc/sec High Speed:  0.370 cc/sec PeakPressure:   250 psi.

[0117] When a normal syringe and needle of the dimensions describedabove are used to inject the same fluid manually, it has been found thatan exit pressure of up to 660 psi or more is generated.

[0118] For other procedures, different syringes, drugs, tubes and/orneedles are selected.

[0119] As discussed above, a critical parameter being monitored by thesubject system is the fluid exit pressure at the tip of the needle,i.e., the pressure within the tissue as the fluid exits from the needle.This is the pressure which is indicated by the graphs of FIGS. 15A and16A. However, this pressure is very difficult to measure directly.Therefore in the present invention rather then taking a directmeasurement, an indirect measurement is obtained. More specifically, thedesired exit or needle pressure Pn is derived from the force indicatedby the cell 78 and the physical characteristics of the system. Moreparticularly, it has been found that the exit pressure during a steadystate (i.e. with the plunger moving at a constant velocity) can beexpressed as follows:

Pn=Ps-dVhn+dVhl-d(Fl+Ft+Fn)

[0120] where

[0121] Ps is the pressure generated at the plunger/fluid interface bythe movement of the plunger;

[0122] Vhn is the velocity head in the needle;

[0123] Vhl is the velocity head in the syringe;

[0124] d is the specific weight of the fluid; and

[0125] Fl, Ft and Fn represent frictional losses due to flow in thesyringe, tube and needle respectively.

[0126] There are some other minor pressure losses in the system whichhave found to be less than 1 and therefore can be ignored.

[0127] The frictional losses are determined empirically and stored aspart of the profile for each element of the system. For example typicalvalues for Fl, Ft and Fn have been found to be:

[0128] Fl=0.1%; Ft=89%; Fn=11% of the total head loss.

[0129] The density of the fluid is known and is usually close to thedensity of water.

[0130] The velocity heads are calculated using the expression:

Vhl=α*Q ² d/[(π/4)² D ⁴(2 g)]

[0131] where α is the kinetic energy factor related to the Reynoldsnumber and for laminar flow has a value of 2;

[0132] Q is the respective fluid flow, as indicated in FIGS. 15A an 16A;

[0133] g is the gravitational constant; and

[0134] D is the inner diameter of the respective member, i.e. thesyringe for Vhl and the needle for Vhn.

[0135] An additional factor for acceleration must be added whenever themotor speeds up or slows down. This factor is given by the followingexpression:

Ms*a/As +Mt*a/At +Mn*a/An

[0136] where Ms, Mt and Mn are the fluid masses respectively in thesyringe, tube and needle and As, At and An are the corresponding crosssectional areas.

[0137] A program for determining the exit pressure (designated in theprogram listing as ‘Needle Pressure’) is attached at the end of thisspecification. As can be seen from this listing, and in the flow chartof FIG. 20, in order to calculate the exit pressure, first the frictionlosses in each of the tree components (the syringe, tube and needle) aredetermined as follows. In step 700 a Reynolds number is determined fromthe flow rate, the component diameter and viscosity. If the Reynoldsnumber is over 2000 (indicating a turbulent flow) then (step 702) aparameter Kinetic Energy Factor is set to 1 and the Friction Loss iscalculated using the Reynolds number (step 704).

[0138] For R<2000 (step 706) the Kinetic Energy Factor is set to 2, anda different expression is used to determine (step 706) the FrictionLoss. (based on the fluid viscosity the flow rate and componentdiameter). In the absence of a flow, the Friction Loss and the KineticEnergy Factor are both set to 0.(708). Next, when the parameters fromall the components are calculated, the flow loss for each component iscalculated, the stopper force 25 is calculated, and all these parametersare used to obtain the exit or needle pressure (step 712).

[0139] Every time the microprocessor 152 checks the pressure (Step 318in FIG. 11), it actually calculates the exit or needle pressure Pn asdiscussed above. FIGS. 16 B and 17B show a normal pressure and anabnormal pressure curve respectively using these expressions.

[0140] Going back to step 302 in FIG. 11, if the device is to be used tocharge the syringe, a charging subroutine is initiated, as indicated inFIG. 18. In step 600 of this Fig. the platform 30 is moved to the homeposition. In step 602 a test is performed to determine if the syringe isto be charged with or without air. If a charging with air is to occurthen in step 604 the platform 30 is positioned for the syringe head inthe position when the syringe is completely full. In step 606 the systemwaits for the syringe to be placed.

[0141] In order to charge a syringe, the system must be connected to asource of fluid such as a vial or bottle. More particularly, as shown inFIG. 19, in order to achieve charging the syringe 90 is connected totube 14 through a three-way valve 700. Valve 700 is used to connect thesystem to fluid source 702 through a pipe 706. For charging the syringe,the valve is positioned so that the fluid source 702 is connected to thesyringe. In the FIG. 19, fluid source 702 is shown upside down so thatit has an air space 706. For charging with air, the syringe plunger 94is positioned as if the syringe was full, i.e. in the position shown inFIG. 19. For a charging without air, the syringe plunger is moved in sothat it is as close as possible to the opposite end as shown at 94A.Once the connections shown in FIG. 19 are completed, the clinician canposition the syringe on the groove 38 and secure it with clamp 40 withthe plunger head engaged by platform 30.

[0142] Referring back to FIG. 18, in step 606 the syringe is nowdetected. In step 608 the syringe is advanced to the empty positionforcing air from the syringe into the source 702, thereby pressurizingit. In step 610 the position is retrieved to an initial positioncorresponding to the volume of fluid to be injected as set by theclinician earlier. In step 612 the clinician is reminded to turn thevalve 700 to couple the syringe 90 to tube 14. The system now returns tostep 308.

[0143] If in step 602 it is determined that charging without is to beperformed then in step 604 the platform 30 is moved to the emptyposition of the syringe. The system then waits for the syringe to beplaced in its position in step 616, after which the system continueswith step 610 as shown.

[0144] The system has been described so far as performing an injectionprocess. However, it is obvious to one skilled in the art that it can beused just as effectively to perform a biopsy, for instance to perform aspinal tap, or other similar anaerobic procedures . Essentially the sameparameters can be used for this process, with some minor modifications.For instance, instead of defining an exit pressure, the clinician nowdefines an entry pressure. Some of the subroutines, such as purging,charging or aspiration are not required for biopsy at all.

[0145] Obviously numerous modifications may be made to this inventionwithout departing from its scope as defined in the appended claims.PROGRAM LISTING uses math, Sys Utils; type T Pressure - Record FlowRate:single; // Cubic Inches/Second (Input) MechanismForce: single; // 1Pounds (DB) {MachineResistancd???} LoadCellForce: single; // Pounds(Input) SyringeForce: single; // Pounds (DB) SyringeDiameter: single; //Inches (Input) SyringeLength: single; // Inches (DB) TubingDiameter:single; // Inches (DB) TubingLength: single; // Inches (DB)NeedleDiameter: single; // Inches (DB) NeedleLength: single; // Inches(DB) SpecificWeight: single; // Slugs/Cubic Inch (DB) Viscosity: single;// No Units (DB)  The term DB indicates that the value of a parameter isretrieved from one of the data bases. Input - means that the parameterhas been calculated previously Calculated - Value calculated by thisroutine} end; The following variables are defined in the course of thisprocess: VelocityLast: single; TimeLast: double; implementation functionCalculatePressure (P:TPressure) :single; const KineticEnergyFactor =2.0; Gravity = 386.4; var KineticEnergyFactorSyringe: single;KineticEnergyFactorNeedle: single; KineticEnergyFactorTubing: single;SyringeFrictionLoss: single; SyringeFlowLoss: single;SyringeVelocityHead: single; NeedleFrictionLoss: single; NeedleFlowLoss:single; NeedleVelocityHead: single; TubingFrictionLoss: single;TubingFlowLoss: single; VelocityConstant: single; StopperForce: single;Reynolds Syringe: single; ReynoldsTubing: single; ReynoldsNeedle:single; NeedlePressure:single; // Value returned Volume, Accel: single;VelocityNow: single; TimeNow: double; begin VelocityConstant :=P.SpecificWeight / (Sgr(PI / 4.0) * 2.0 * Gravity); try ReynoldsSyringe:= P.Flowrate / (PI * P.SyringeDiameter * (P.Viscosity / 4)); ifReynoldsSyringe >= 2000.0 then begin KineticEnergyFactorSyringe : = 1.0;SyringeFrictionLoss := 0.25 / sqr(log10 ( 0.0000012 / (3.7 *P.SyringeDiameter) + (5.74 / Power(ReynoldsSyringe, 0.9)))); end elsebegin KineticEnergyFactorSyringe := 2.0; SyringeFrictionLoss := (16 *P.Viscosity * PI * P.SyringeDiameter) / P.Flowrate end; exceptSyringeFrictionLoss := 0; KineticEnergyFactorSyringe := 0; end; tryReynoldsTubing := P.Flowrate / (PT * P.TubingDiameter * (P.Viscosity /4)); if ReynoldsTubing >= 2000.0 then begin KineticEnergyFactorTubing :=1.0; TubingFrictionLoss := 0.25 / sqr(log10 ( 0.0000012 / (3.7 *P.TubingDiameter) + (5.74 / Power(ReynoldsTubing, 0.9)))); end elsebegin KineticEnergyFactorTubing := 2.0; TubingFrictionLoss := (16 *P.Viscosity * PI * P.TubingDiameter) / P.Flowrate end; exceptTubingFrictionLoss := 0; KineticEnergyFactorTubing := 0; end; tryReynoldsNeedle := P.Flowrate / (PI * P.NeedleDiameter * (P.Viscosity /4)); if ReynoldsNeedle >= 2000.0 then begin KineticEnergyFactorNeedle :=1.0; NeedleFrictionLoss := 0.25 / sqr(log10 ( 0.0000012 / (3.7 *P.NeedleDiameter) + (5.74 / Power(ReynoldsNeedle, 0.9)))); end elsebegin KineticEnergyFactorNeedle := 2.0; NeedleFrictionLoss := (16 *P.Viscosity * PI * P.NeedleDiameter) / P.Flowrate end; exceptNeedleFrictionLoss := 0; KineticEnergyFactorNeedle := 0; end; Volume :=((PI / 4) * sqr(P.SyringeDiameter) * P.SyringeLength) + ((PT / 4) *sqr(P.TubingDiameter) * P.TubingLength) + ((PI / 4) *sgr(P.NeedleDiameter) * P.NeedleLength); VelocityNow := P.FlowRate /((PI / 4) * Sqr (P. SyringeDiameter)); TimeNow now := now * 24 * 60 *60; if (TimeLast > 0) and (not P.TestMode) then begin      // First timeentered switch Accel := ((P.SpecificWeight * Volume) / Gravity) *((VelocityLast - VelocityNow) / (TimeNow - TimeLast)); end else beginAccel := 0; end; VelocityLast := VelocityNow; // Save for next tineTimeLast := TimeNow; NeedleVelocityHead := (VelocityConstant *KineticEnergyFactorNeedle) * (Sqr(P.FlowRate) / Power(P.NeedleDiameter,4.0)); SyringeVelocityHead := (VelocityConstant *KineticEnergyFactorSyringe) * (Sqr(P.FlowRate) /Power(P.SyringeDiameter, 4.0)); SyringeFlowLoss :=(SyringeFrictionLoss * P.SyringeLength * Sqr(P.FlowRate)) /(P.SyringeDiameter * 2.0 * Gravity * Sqr(PI * Sqr(P.SyringeDiameter) /4.0)) ; TubingFlowLoss := (TubingFrictionLoss * P.TubingLength *Sqr(P.FlowRate)) / (P.TubingDiameter * 2.0 * Gravity * Sqr(PI *Sqr(P.TubingDiameter) / 4.0)) ; NeedleFlowLoss := (NeedleFrictionLoss *P.NeedleLength * Sqr(P.FlowRate)) / (P.NeedleDiameter * 2.0 * Gravity *Sqr(PI * Sqr(P.NeedleDiameter) / 4.0)) ; StopperForce :=P.LoadCellForce - P.SyringeForce - P.MechanismForce; //StopperForce :=P.LoadCellForce; NeedlePressure (StopperForce / (PI *sqr(P.SyringeDiameter/2))) - NeedleVelocityHead + SyringeVelocityHead(P.SpecificWeight * (SyringeFlowLoss + TubingFlowLoss + NeedleFlowLoss)− (Accel / (PI * sqr(P.SyringeDiameter / 2)))); end.

We claim:
 1. An automatic injection device arranged to inject a fluidinto a patient comprising: a pump arranged to pump fluid in accordancewith commands; a delivery unit receiving said fluid and delivering thesame to the patient; a controller having a memory used to store aplurality of profiles defining operational parameters for the deliveryof the fluid; and a selector used to select said operational parameters.2. The device of claim 1 wherein said profiles define several modes ofoperation, each mode being related to a rate of flow of said fluid as itis delivered to the patient.
 3. The device of claim 1 wherein saiddelivery unit has physical characteristics defining fluid flow, andwherein said memory is used to store said physical characteristic. 4.The device of claim 3 further comprising a characteristic sensor adaptedto sense one of said characteristics.
 5. The device of claim 3 whereinsaid selector is adapted to select one of said physical characteristics.6. The device of claim 1 wherein said profiles define a fluidcharacteristic of said fluid.
 7. The device of claim 6 wherein saidfluid characteristic is selected from a fluid viscosity, fluid specificweight and fluid temperature.
 8. An automatic injection devicecomprising: a syringe having syringe characteristics and adapted to holda fluid; a plunger arranged to reciprocate in said syringe to effectfluid flow in and out of said syringe; a driver coupled to said plunger;a controller adapted to generate control commands for said driver tooperate said plunger in accordance with a preselected profile; a memoryarranged to store a plurality of profiles; and a selector arranged toselect said preselected profile from said memory.
 9. The automaticinjection device of claim 8 wherein said preselected profile defines atime dependent sequence of operation during which fluid flows from saidsyringe at predetermined rates.
 10. The automatic injection device ofclaim 9 further comprising a pressure sensor adapted to measure a fluidpressure associated with the fluid from said syringe, and wherein saidcontroller is adapted to control the fluid flow in accordance with saidfluid pressure.
 11. The automatic injection device of claim 10 whereinsaid profile includes a fluid pressure limit and wherein said controlleris adapted to limit said fluid rate in accordance with said fluidpressure limit.
 12. The automatic injection device of claim 8 furthercomprising a needle shaped to be inserted in tissues and a tube couplingsaid syringe to said needle.
 13. The automatic injection device of claim12 wherein said needle is defined by a needle size, wherein said memoryincludes a plurality of needle sizes, and wherein said selector isarranged for the selection of the needle size from said memory.
 14. Theautomatic injection device of claim 12 wherein said tube is defined by atube size, wherein said memory includes a plurality of tube sizes andsaid selector is arranged for the selection of the tube size from saidmemory.
 15. The automatic injection device of claim 12 wherein saidsyringe is defined by a syringe size and type, wherein said memoryincludes a plurality of syringe sizes and types and wherein selector isarranged for the selection of the syringe size and type.
 16. A method ofinjecting a fluid into a patient using an automatic injection devicehaving a fluid source, and a pump for selectively delivering fluid fromsaid source to said patient, said device further including a memory witha profiles, to said patient comprising: selecting a profile from saidmemory; and delivering fluid to the patient in accordance with saidprofile.
 17. The method of claim 16 wherein said device includes apressure sensor detecting a fluid pressure, further comprising:measuring a current fluid pressure; and controlling fluid flow inaccordance with said fluid pressure.
 18. The method of claim 16 furthercomprising a delivery member adapted to deliver said fluid and includinga syringe, a tube and a needle having respective syringe, tube andneedle sizes, further comprising selecting said syringe, tube and needlesize prior to the delivery of said fluid.
 19. The method of claim 18wherein said sizes are selected manually.
 20. The method of claim 19wherein at least one of said sizes is stored in the memory, and whereinsaid one size is selected from said memory.
 21. The method of claim 18wherein tube size includes one of a tube length and tube inner diameter.22. The method of claim 18 wherein said needle size includes one of aneedle length and a needle diameter.
 23. The method of claim 18 whereinsaid syringe size includes one of syringe type and a syringe size.